Piston.



GEORGE L. COWAN, 0F EAST RYEGATE, VERMONT, ASSIGNOR TO HOLYOKE MACHINE COMPANY, 0F HOLYOKE, MASSACHUSETTS, A CORPORATION OF MASSA@HUSETTS.Y

PISTON.

Specification of Letters Patent.

Patented Jan. 29,1918.

Application led April 28, 1916; Serial No. 94,111.

To all whom z't may concern:

Be it known that I, GEORGE L. CowAN, a citizen of the United States of America, residing at East Ryegate, in the county of Caledonia and State of Vermont, have invented certain new and useful improvements in Pistons, of which the following is a specification.

rhis invention relates to improvements in pistons that are designed to be used in pulp grinding machines, although I do not limity myself to the pulp grinding art.

An object of theinvention lis to pro-vide a piston which will automatically expand or move the ring of packing material out ward against the inner surface of the cylinder in v which the piston reciprocates. Broadly, the invention comprises a piston formed with spaced .plates or heads, each of the heads having inwardly opening valves to permit the entrance of water, or other fluid, under pressure, to the interior space between the plates, a rim composed of arcshaped members adapted to move radially outwardly against the packing material, and means for permitting the fluid, under pressure, to gain access to the chamber between the plates in which the arc-shaped members are located, whereby these members, as they move outward, will, under pressure, in turn, compress the packing material against the inner walls of the cylinder for forming a fluid tight joint between the packing and the walls of the cylinder. Means is also provided for guiding the arc-shaped members and retaining the same in place during their radial movements.

Referring to the drawings:

Figure 1 is a general assembly view illus! trating the application of the invention to a pulp grinding machine, the upper and lower plates of the piston being shown in section to illustrate the interior arrangement of the parts;

Fig. 2 is a plan view of the interior of the piston with one of the cover plates removed showing tlie circular-shaped rib integral with the other plate with the openings therethrough; the arc-shaped members for forcing the ring of packing material outward and having stems attached thereto which extends through the openings in the rib, also illustrating one of the inwardly opening valves within the circular rib;

Fig. 8 is a detail view of a portion of piston, the valve being illustrated in itsop'en position;

Fig. 4 is a transverse sectional view taken on a` vertical plane on the broken line 4 4 of Fig. 2, showing the integral hub and rib, the inwardly opening valve in one plate and one of the arc-shaped members with its stem passing through the rib and the spring on the stem between the arc-shaped member and the rib for normally'retaining this member in an outward position, and, the packing material in section.

Referring to the drawings in detail: The cylinder in which the piston operates is indicated at 1, the chamber in which the blocks of wood are placed is indicated at 2, and the follower at 8. The piston that is attached to the pistonr rod 4 includes two plates or heads 5 and 6. Flate 5 is formed with an integral circular rib 7 and an integral hub S for attaching the piston rod 4 to the piston by inserting the same in the opening 9 as illustrated in Fig. 1. The rib' 7 is formed with radially arranged ports or openings 1-0 and other openings 11, the openings 10 are for the purpose of allowing fluid, under pressure, to pass'therethrough, as will be explained in thel operation of the piston. The rib 7, it will `be observed is only attached to the plate at one edge. 12 designates a plurality of arcshaped members that are loosely mounted on the inner face of the plate 5, as shown in Fig. 4. Se cured to the arc-shaped members are rods 13 which extend inwardly and pass through the openings 11 and mounted on the rods 13 are springs 14, that are normally under compression for forcing the arc-shaped members outward against the ring of paclring material 15 that extends around the outer surface of the arc-shaped members 12.

The plates 5 and 6 are provided with valves 1,6 and 17 'which open inwardly into the space between the plates. These valves art secured in place by means of the bolts 18 that are threaded into the plates 5 and 6 and, between the head of the bolts and the valves is placed a compression spring 19 for the purpose of normally holding the valves closed. The plate or head v6 is secured to the plate 5, as stated above, by means of the piston rod 4l. rlhe vertical height of the in tegral rib 7 and hub 8 is such that when the plate or cover G is secured in place and rests on the circular rib 7 and the hub 8, the arcshaped members .l2 will have Jfree radial movements between the plates,

ln the operation et the valve, considering the piston at the end of its travel or upper position, as shown in Fig. l, when water, or other fluid under pressure, flows through the port 20 to the chamber Q1, the valve 17 in the head 6 will open inwardly allowing the fluid under pressure to through the openings 22 and into the chamber or space 23 within the annular rib i. From this chamber it flows through the ports l() into the annular space occupied by the arcshaped members l2. rlhese members will be forced radially outward by the fluid under pressure and against the packing material. T his pressure continues until the piston reaches the lower end of its travel and as it is driven backward by the iiuid under pressure through the port 2a the valve 16 will then open permitting the iiuid under pres sure to pass through the openings Q2 and ports l0 into the space occupied by the arcshaped members l2 as before and maintaining the ring of packing material l5 in an outward position tightly against the inner walls oi? the cylinder l. It will thus be seen that there is a continuous pressure at all times exerted by means of the fluid on the arc-shaped members l2 to maintain. the packing material tight against the inner surface of the cylinder l. rthis construction of valve automatically takes care of and avoids the necessity ot' repacking the piston when it shows signs of leakage. It also permits the piston to be used until the packing material is entirely worn. away. ln case of cluding separable plates or heads spaced l trom each other, each plate having an inwardly opening valve, said valves being retained in a guided position by means of bolts located between the heads and secured to the separable plates, a compression spring between the head of each of the bolts and the valves to maintain the same closed, one of the heads having a hub for attaching the piston rod thereto and an annular ring or rib of the same height as the hub and having ports therethrough to permit fluid under pressure to pass therethrough and other openings for guiding arc-shaped expansion members toward and away from the packing material, said inwardly opening valves being located within the annular ring, said arc-shaped members being located near the outer edge et the plates, whereby as the piston reciprocates tluid under pressure will pass to the interior of the piston and through the ports in the rib, for the purpose of moving the arc-shaped expansion members against the packing material, one of the heads resting on the hub and ring for spacing the plates yet permitting the arc shaped expansion members and packing ma terial to have tree movement between the heads.

GEORGE L. COVVAN.

Copies et this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

